Bad Air Days in St. Tammany Parish, Louisiana: under 1 a Year
under 1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 756 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (29% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in May and January and March and June. Averaged over 2016 to 2025.
Is a purifier worth it here?
- Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
- On the odd bad day, check AirNow and keep windows shut.
Better or worse than it was
The worst recent year was 2024, with 1 bad day on 362 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2024-01-01 | 186 | PM2.5 |
| 2017-05-09 | 129 | Ozone |
| 2016-05-08 | 119 | Ozone |
| 2023-05-19 | 105 | Ozone |
| 2025-03-11 | 105 | Ozone |
An ordinary day in St. Tammany
Across 3,626 monitored days from 2016 to 2025, the air in St. Tammany Parish rated Good on 77% of them, more often than the 72% typical of monitored counties, and Moderate on 23%. The median day sat at AQI 40; one day in ten went above 58.
The pollutant setting the AQI on an ordinary day here:
- ozone57%2,050 days
- fine particles (PM2.5)43%1,576 days
St. Tammany Parish by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 363 | 315 | 47 | 1 | 0 | 37 | 105 |
| 2024 | 362 | 291 | 70 | 1 | 1 | 39 | 186 |
| 2023 | 365 | 248 | 116 | 1 | 0 | 42 | 105 |
| 2022 | 365 | 277 | 87 | 1 | 0 | 41 | 103 |
| 2021 | 352 | 288 | 64 | 0 | 0 | 37 | 71 |
| 2020 | 364 | 268 | 96 | 0 | 0 | 39 | 90 |
| 2019 | 363 | 266 | 97 | 0 | 0 | 41 | 84 |
| 2018 | 365 | 280 | 84 | 1 | 0 | 38 | 101 |
| 2017 | 364 | 271 | 92 | 1 | 0 | 41 | 129 |
| 2016 | 363 | 271 | 91 | 1 | 0 | 41 | 119 |
| 2015 | 365 | 249 | 116 | 0 | 0 | 43 | 100 |
| 2014 | 365 | 229 | 127 | 9 | 0 | 45 | 143 |
| 2013 | 365 | 213 | 148 | 4 | 1 | 46 | 154 |
| 2012 | 359 | 217 | 139 | 3 | 0 | 46 | 122 |
| 2011 | 365 | 216 | 134 | 15 | 0 | 46 | 143 |
| 2010 | 362 | 183 | 174 | 5 | 2 | 50 | 159 |
*2025 may be a partial year in EPA's file.
Elsewhere in Louisiana
How this is counted
A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.